Observing tropospheric water vapor by radio occultation using the Global Positioning System

Kursinski, E. R.; Hajj, G. A.; Hardy, Kenneth R.; Romans, L.J.; Schofield, J. T.

doi:10.1029/95gl02127

Cited by 84 publications

(75 citation statements)

References 16 publications

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“…Recent developments of the Global Navigation Satellite Systems (GNSS), such as the Global Positioning System (GPS), Russian Glonass, European Galileo and Chinese Beidou/Compass, have offered exciting potential for meteorological research (Fu et al, 2007;Kursinski et al, 1995;Yunck and Melbourne, 1995;Yunck et al, 2000). Observations from GPS Continuously Operating Reference Stations (CORS) networks have been well utilized for generating useful atmospheric water vapour information (Liou et al, 2000;Rocken et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

An investigation of atmospheric temperature profiles in the Australian region using collocated GPS radio occultation and radiosonde data

Zhang

Silcock

et al. 2011

Atmos. Meas. Tech.

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Abstract. GPS radio occultation (RO) has been recognised as an alternative atmospheric upper air observation technique due to its distinct features and technological merits. The CHAllenging Minisatellite Payload (CHAMP) RO satellite and FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) RO constellation together have provided about ten years of high quality global coverage RO atmospheric profiles. This technique is best used for meteorological studies in the difficult-toaccess areas such as deserts and oceans. To better understand and use RO data, effective quality assessment using independent radiosonde data and its associated collocation criteria used in tempo-spatial domain are important. This study compares GPS RO retrieved temperature profiles from both CHAMP (between May 2001 and October 2008) and FORMOSAT-3/COSMIC (between July 2006 and December 2009) with radiosonde data from 38 Australian radiosonde stations. The overall results show a good agreement between the two data sets. Different collocation criteria within 3 h and 300 km between the profile pairs have been applied and the impact of these different collocation criteria on the evaluation results is found statistically insignificantly. The CHAMP and FORMOSAT-3/COSMIC temperature profiles have been evaluated at 16 different pressure levels and the differences between GPS RO and radiosonde at different levels of the atmosphere have been studied. The result shows that the mean temperature difference between radiosonde and CHAMP is 0.39 • C (with a standard deviation of 1.20 • C) and the one Correspondence to: E. Fu (f.fu@bom.gov.au) between radiosonde and FORMOSAT-3/COSMIC is 0.37 • C (with a standard deviation of 1.24 • C). Different collocation criteria have been applied and insignificant differences were identified amongst the results.

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Section: Introductionmentioning

confidence: 99%

An investigation of atmospheric temperature profiles in the Australian region using collocated GPS radio occultation and radiosonde data

Zhang

Silcock

et al. 2011

Atmos. Meas. Tech.

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“…2.5 Establishing data set accuracy Kursinski et al (1995) estimated that occultation water vapor pressure profiles at the tropics have a precision between 10 and 20 % below 7.0 km altitude assuming temperature errors of 1.5 K, surface pressure errors of 3 mbar, and refractivity errors of < 0.2 %, which translate to a SH precision of < 0.25 g kg −1 at 700 hPa and < 0.03 g kg −1 at 400 hPa, given a mean SH of 4.0 g kg −1 at 700 hPa and 1.0 g kg −1 at 400 hPa between January 2007 and December 2015. Kursinski and Hajj (2001) determined that the precision of individual occultation SH profiles is ∼ 0.20-0.50 g kg −1 in the middle-to-lower troposphere.…”

Section: Atmospheric Infrared Soundermentioning

confidence: 99%

Comparisons of the tropospheric specific humidity from GPS radio occultations with ERA-Interim, NASA MERRA, and AIRS data

Vergados

Mannucci

et al. 2018

Atmos. Meas. Tech.

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Abstract. We construct a 9-year data record (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015) of the tropospheric specific humidity using Global Positioning System radio occultation (GPS RO) observations from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission. This record covers the ±40 • latitude belt and includes estimates of the zonally averaged monthly mean specific humidity from 700 up to 400 hPa. It includes three major climate zones: (a) the deep tropics (±15 • ), (b) the trade winds belts (±15-30 • ), and (c) the subtropics (±30-40 • ). We find that the RO observations agree very well with the European Centre for Medium-Range Weather Forecasts Re-Analysis Interim (ERA-Interim), the Modern-Era Retrospective Analysis for Research and Applications (MERRA), and the Atmospheric Infrared Sounder (AIRS) by capturing similar magnitudes and patterns of variability in the monthly zonal mean specific humidity and interannual anomaly over annual and interannual timescales. The JPL and UCAR specific humidity climatologies differ by less than 15 % (depending on location and pressure level), primarily due to differences in the retrieved refractivity. In the middle-to-upper troposphere, in all climate zones, JPL is the wettest of all data sets, AIRS is the driest of all data sets, and UCAR, ERA-Interim, and MERRA are in very good agreement, lying between the JPL and AIRS climatologies. In the lower-to-middle troposphere, we present a complex behavior of discrepancies, and we speculate that this might be due to convection and entrainment. Conclusively, the RO observations could potentially be used as a climate variable, but more thorough analysis is required to assess the structural uncertainty between centers and its origin.

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“…The COSMIC occultation is a joint Taiwan/US science mission for weather, climate, space weather and geodetic research (Yen et al, 2007). Radio occultation technique has been widely applied for meteorology study (Kursinski et al, 1995;Yen et al, 2010;Anthes et al, 2008).…”

Section: Data Collectionmentioning

confidence: 99%

GNSS troposphere tomography based on two-step reconstructions using GPS observations and COSMIC profiles

2013

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Abstract. Traditionally, balloon-based radiosonde soundings are used to study the spatial distribution of atmospheric water vapour. However, this approach cannot be frequently employed due to its high cost. In contrast, GPS tomography technique can obtain water vapour in a high temporal resolution. In the tomography technique, an iterative or non-iterative reconstruction algorithm is usually utilised to overcome rank deficiency of observation equations for water vapour inversion. However, the single iterative or noniterative reconstruction algorithm has their limitations. For instance, the iterative reconstruction algorithm requires accurate initial values of water vapour while the non-iterative reconstruction algorithm needs proper constraint conditions. To overcome these drawbacks, we present a combined iterative and non-iterative reconstruction approach for the threedimensional (3-D) water vapour inversion using GPS observations and COSMIC profiles. In this approach, the noniterative reconstruction algorithm is first used to estimate water vapour density based on a priori water vapour information derived from COSMIC radio occultation data. The estimates are then employed as initial values in the iterative reconstruction algorithm. The largest advantage of this approach is that precise initial values of water vapour density that are essential in the iterative reconstruction algorithm can be obtained. This combined reconstruction algorithm (CRA) is evaluated using 10-day GPS observations in Hong Kong and COSMIC profiles. The test results indicate that the water vapor accuracy from CRA is 16 and 14 % higher than that of iterative and non-iterative reconstruction approaches, respectively. In addition, the tomography results obtained from the CRA are further validated using radiosonde data. Results indicate that water vapour densities derived from the CRA agree with radiosonde results very well at altitudes above 2.5 km. The average RMS value of their differences above 2.5 km is 0.44 g m −3 .

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Observing tropospheric water vapor by radio occultation using the Global Positioning System

Cited by 84 publications

References 16 publications

An investigation of atmospheric temperature profiles in the Australian region using collocated GPS radio occultation and radiosonde data

An investigation of atmospheric temperature profiles in the Australian region using collocated GPS radio occultation and radiosonde data

Comparisons of the tropospheric specific humidity from GPS radio occultations with ERA-Interim, NASA MERRA, and AIRS data

GNSS troposphere tomography based on two-step reconstructions using GPS observations and COSMIC profiles

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